    Patent Literature 1: JP 2004-190662 A (U.S. Pat. No. 7,027,913 B2)
Patent Literature 1 proposes a vehicle control system including a sensor ECU, a transmission control module (TCM) ECU, and an ignition ECU, for example. In the vehicle control system, the information on crank angle is given from the sensor ECU to the TCM ECU; and the information on ignition timing is given from the TCM ECU to the ignition ECU. Then, the ignition ECU controls the igniter to synchronize with the crank angle.
Thus, the vehicle control system in Patent Literature 1 has a configuration to move the information from the sensor ECU to the TCM ECU, and then from the TCM ECU to the ignition ECU. In contrast, another configuration may be supposed which inputs a crank signal into each of two ECUs which control a target motor such as an engine. The crank signal is provided to have a signal level, which reciprocate between the high level and the low level each time a crank rotates by a predetermined angle. This configuration requires each ECU to synchronize with the crank signal, in order to control the motor with high precision.
To that end, a first ECU inputs a pulse count number to a second ECU. The pulse count number is obtained by counting the number of pulses included in the crank signal; the number of pulses is a pulse count that is the number of rising edges that occur when the signal level of the crank signal changes from the low level to the high level. Then, the second ECU determines whether the pulse count number inputted from the first ECU is equal to a pulse count number that is calculated internally by the second ECU. This enables a determination as to whether the first microcomputer and the second microcomputer synchronize with the crank signal. Such a configuration needs an input time period (i.e., a processing time period) up to the time when the pulse count number from the first ECU is inputted to the second ECU.
Thereby, a high velocity revolution of an engine may cause the processing time to become longer than a pulse period of the crank signal. Such a case determines that the first microcomputer and the second microcomputer do not synchronize with the crank signal even though the first microcomputer and the second microcomputer synchronize with the crank signal. Such a defect or mistake may be solvable by adopting a high-speed processing ECU or a high-speed communication network between ECUs. However, this needs additional costs.